Fix inlay hint cursor (#54048)

https://github.com/user-attachments/assets/e7a7903b-e133-4fbf-9267-3ebb17f867ff

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #43132

Release Notes:

- Fixed inlay hints navigating to the wrong position

crates/editor/src/display_map.rs

@@ -2050,6 +2050,21 @@ impl DisplaySnapshot {
         DisplayPoint(self.block_snapshot.clip_point(point.0, bias))
     }
 
+    pub fn inlay_bias_at(&self, point: DisplayPoint) -> Option<Bias> {
+        let wrap_point = self.block_snapshot.to_wrap_point(point.0, Bias::Left);
+        let tab_point = self.block_snapshot.to_tab_point(wrap_point);
+        let (fold_point, _, _) = self
+            .block_snapshot
+            .tab_snapshot
+            .tab_point_to_fold_point(tab_point, Bias::Left);
+        let inlay_point =
+            fold_point.to_inlay_point(&self.block_snapshot.tab_snapshot.fold_snapshot);
+        self.block_snapshot
+            .tab_snapshot
+            .fold_snapshot
+            .inlay_bias_at_point(inlay_point)
+    }
+
     pub fn clip_at_line_end(&self, display_point: DisplayPoint) -> DisplayPoint {
         let mut point = self.display_point_to_point(display_point, Bias::Left);
 

crates/editor/src/display_map/inlay_map.rs

@@ -1094,6 +1094,15 @@ impl InlaySnapshot {
         }
     }
 
+    pub fn inlay_bias_at_point(&self, point: InlayPoint) -> Option<Bias> {
+        let mut cursor = self.transforms.cursor::<Dimensions<InlayPoint, Point>>(());
+        cursor.seek(&point, Bias::Left);
+        match cursor.item() {
+            Some(Transform::Inlay(inlay)) => Some(inlay.position.bias()),
+            _ => None,
+        }
+    }
+
     #[ztracing::instrument(skip_all)]
     pub fn text_summary(&self) -> MBTextSummary {
         self.transforms.summary().output

crates/editor/src/editor_tests.rs

@@ -31506,6 +31506,96 @@ async fn test_inlay_hints_request_timeout(cx: &mut TestAppContext) {
         .unwrap();
 }
 
+#[gpui::test]
+async fn test_click_on_parameter_inlay_hint_places_cursor_correctly(cx: &mut TestAppContext) {
+    use crate::inlays::inlay_hints::tests::{cached_hint_labels, visible_hint_labels};
+
+    let mut cx = EditorLspTestContext::new_rust(
+        lsp::ServerCapabilities {
+            inlay_hint_provider: Some(lsp::OneOf::Left(true)),
+            ..Default::default()
+        },
+        cx,
+    )
+    .await;
+
+    cx.update(|_, cx| {
+        SettingsStore::update_global(cx, |store, cx| {
+            store.update_user_settings(cx, &|settings: &mut SettingsContent| {
+                settings.project.all_languages.defaults.inlay_hints =
+                    Some(InlayHintSettingsContent {
+                        enabled: Some(true),
+                        show_parameter_hints: Some(true),
+                        show_type_hints: Some(true),
+                        edit_debounce_ms: Some(0),
+                        scroll_debounce_ms: Some(0),
+                        ..Default::default()
+                    })
+            });
+        });
+    });
+
+    cx.set_state("fn foo(value: i32) {} fn main() { foo(ˇ42); }");
+
+    // Buffer: `fn foo(value: i32) {} fn main() { foo(42); }`
+    // The parameter hint "value:" appears before "42"
+    let hint_start_offset = cx.ranges("fn foo(value: i32) {} fn main() { foo(ˇ42); }")[0].start;
+    let hint_position = cx.to_lsp(MultiBufferOffset(hint_start_offset));
+    let hint_label = "value:";
+    let expected_uri = cx.buffer_lsp_url.clone();
+    cx.lsp
+        .set_request_handler::<lsp::request::InlayHintRequest, _, _>(move |params, _| {
+            let expected_uri = expected_uri.clone();
+            async move {
+                assert_eq!(params.text_document.uri, expected_uri);
+                Ok(Some(vec![lsp::InlayHint {
+                    position: hint_position,
+                    label: lsp::InlayHintLabel::String(hint_label.to_string()),
+                    kind: Some(lsp::InlayHintKind::PARAMETER),
+                    text_edits: None,
+                    tooltip: None,
+                    padding_left: None,
+                    padding_right: Some(true),
+                    data: None,
+                }]))
+            }
+        })
+        .next()
+        .await;
+    cx.background_executor.run_until_parked();
+
+    cx.update_editor(|editor, _window, cx| {
+        let expected_labels = vec!["value: ".to_string()];
+        assert_eq!(expected_labels, cached_hint_labels(editor, cx));
+        assert_eq!(expected_labels, visible_hint_labels(editor, cx));
+    });
+
+    // The cursor is at `4` in `42`. The parameter hint "value: " appears just
+    // before it in display space. We'll click a few characters to the left of
+    // the cursor position to land inside the inlay hint text.
+    let cursor_display_point = cx.update_editor(|editor, _window, cx| {
+        editor
+            .selections
+            .newest_display(&editor.display_snapshot(cx))
+            .head()
+    });
+    let cursor_pixel = cx.pixel_position_for(cursor_display_point);
+    let em_width =
+        cx.update_editor(|editor, _, _| editor.last_position_map.as_ref().unwrap().em_layout_width);
+    // Click 3 characters to the left of the cursor, which lands inside the
+    // "value: " inlay hint text.
+    let click_position = gpui::Point {
+        x: cursor_pixel.x - em_width * 3.0,
+        y: cursor_pixel.y,
+    };
+    cx.simulate_click(click_position, Modifiers::none());
+    cx.background_executor.run_until_parked();
+
+    // The cursor should be placed after the `(`, at the `4` in `42`,
+    // NOT before the `(`.
+    cx.assert_editor_state("fn foo(value: i32) {} fn main() { foo(ˇ42); }");
+}
+
 #[gpui::test]
 async fn test_newline_replacement_in_single_line(cx: &mut TestAppContext) {
     init_test(cx, |_| {});

crates/editor/src/element.rs

@@ -843,7 +843,7 @@ impl EditorElement {
             }
         }
 
-        let position = point_for_position.previous_valid;
+        let position = point_for_position.nearest_valid;
         if let Some(mode) = Editor::columnar_selection_mode(&modifiers, cx) {
             editor.select(
                 SelectPhase::BeginColumnar {
@@ -898,7 +898,7 @@ impl EditorElement {
             {
                 let point_for_position = position_map.point_for_position(event.position);
                 editor.set_gutter_context_menu(
-                    point_for_position.previous_valid.row(),
+                    point_for_position.nearest_valid.row(),
                     None,
                     event.position,
                     window,
@@ -916,7 +916,7 @@ impl EditorElement {
         mouse_context_menu::deploy_context_menu(
             editor,
             Some(event.position),
-            point_for_position.previous_valid,
+            point_for_position.nearest_valid,
             window,
             cx,
         );
@@ -935,7 +935,7 @@ impl EditorElement {
         }
 
         let point_for_position = position_map.point_for_position(event.position);
-        let position = point_for_position.previous_valid;
+        let position = point_for_position.nearest_valid;
 
         editor.select(
             SelectPhase::BeginColumnar {
@@ -977,7 +977,7 @@ impl EditorElement {
                 if event.position == *click_position {
                     editor.select(
                         SelectPhase::Begin {
-                            position: point_for_position.previous_valid,
+                            position: point_for_position.nearest_valid,
                             add: false,
                             click_count: 1, // ready to drag state only occurs on click count 1
                         },
@@ -1001,7 +1001,7 @@ impl EditorElement {
                         || cfg!(not(target_os = "macos")) && event.modifiers.control);
                     editor.move_selection_on_drop(
                         &selection.clone(),
-                        point_for_position.previous_valid,
+                        point_for_position.nearest_valid,
                         is_cut,
                         window,
                         cx,
@@ -1037,7 +1037,7 @@ impl EditorElement {
             if EditorSettings::get_global(cx).middle_click_paste {
                 if let Some(text) = cx.read_from_primary().and_then(|item| item.text()) {
                     let point_for_position = position_map.point_for_position(event.position);
-                    let position = point_for_position.previous_valid;
+                    let position = point_for_position.nearest_valid;
 
                     editor.select(
                         SelectPhase::Begin {
@@ -1166,7 +1166,7 @@ impl EditorElement {
         if !editor.has_pending_selection() {
             let drop_anchor = position_map
                 .snapshot
-                .display_point_to_anchor(point_for_position.previous_valid, Bias::Left);
+                .display_point_to_anchor(point_for_position.nearest_valid, Bias::Left);
             match editor.selection_drag_state {
                 SelectionDragState::Dragging {
                     ref mut drop_cursor,
@@ -1210,7 +1210,7 @@ impl EditorElement {
                         editor.selection_drag_state = SelectionDragState::None;
                         editor.select(
                             SelectPhase::Begin {
-                                position: click_point.previous_valid,
+                                position: click_point.nearest_valid,
                                 add: false,
                                 click_count: 1,
                             },
@@ -1219,7 +1219,7 @@ impl EditorElement {
                         );
                         editor.select(
                             SelectPhase::Update {
-                                position: point_for_position.previous_valid,
+                                position: point_for_position.nearest_valid,
                                 goal_column: point_for_position.exact_unclipped.column(),
                                 scroll_delta,
                             },
@@ -1233,7 +1233,7 @@ impl EditorElement {
         } else {
             editor.select(
                 SelectPhase::Update {
-                    position: point_for_position.previous_valid,
+                    position: point_for_position.nearest_valid,
                     goal_column: point_for_position.exact_unclipped.column(),
                     scroll_delta,
                 },
@@ -1260,7 +1260,7 @@ impl EditorElement {
         editor.show_mouse_cursor(cx);
 
         let point_for_position = position_map.point_for_position(event.position);
-        let valid_point = point_for_position.previous_valid;
+        let valid_point = point_for_position.nearest_valid;
 
         // Update diff review drag state if we're dragging
         if editor.diff_review_drag_state.is_some() {
@@ -6688,7 +6688,7 @@ impl EditorElement {
                         let snapshot = editor.snapshot(window, cx);
                         let anchor = snapshot
                             .display_snapshot
-                            .display_point_to_anchor(point_for_position.previous_valid, Bias::Left);
+                            .display_point_to_anchor(point_for_position.nearest_valid, Bias::Left);
                         editor.change_selections(
                             SelectionEffects::scroll(Autoscroll::top_relative(line_index)),
                             window,
@@ -11902,6 +11902,7 @@ pub(crate) struct PositionMap {
 pub struct PointForPosition {
     pub previous_valid: DisplayPoint,
     pub next_valid: DisplayPoint,
+    pub nearest_valid: DisplayPoint,
     pub exact_unclipped: DisplayPoint,
     pub column_overshoot_after_line_end: u32,
 }
@@ -11971,12 +11972,23 @@ impl PositionMap {
         let previous_valid = self.snapshot.clip_point(exact_unclipped, Bias::Left);
         let next_valid = self.snapshot.clip_point(exact_unclipped, Bias::Right);
 
+        let nearest_valid = if previous_valid == next_valid {
+            previous_valid
+        } else {
+            match self.snapshot.inlay_bias_at(exact_unclipped) {
+                Some(Bias::Left) => next_valid,
+                Some(Bias::Right) => previous_valid,
+                None => previous_valid,
+            }
+        };
+
         let column_overshoot_after_line_end =
             (x_overshoot_after_line_end / self.em_layout_width) as u32;
         *exact_unclipped.column_mut() += column_overshoot_after_line_end;
         PointForPosition {
             previous_valid,
             next_valid,
+            nearest_valid,
             exact_unclipped,
             column_overshoot_after_line_end,
         }
@@ -12006,12 +12018,23 @@ impl PositionMap {
         let previous_valid = self.snapshot.clip_point(exact_unclipped, Bias::Left);
         let next_valid = self.snapshot.clip_point(exact_unclipped, Bias::Right);
 
+        let nearest_valid = if previous_valid == next_valid {
+            previous_valid
+        } else {
+            match self.snapshot.inlay_bias_at(exact_unclipped) {
+                Some(Bias::Left) => next_valid,
+                Some(Bias::Right) => previous_valid,
+                None => previous_valid,
+            }
+        };
+
         let column_overshoot_after_line_end =
             (x_overshoot_after_line_end / self.em_layout_width) as u32;
         *exact_unclipped.column_mut() += column_overshoot_after_line_end;
         PointForPosition {
             previous_valid,
             next_valid,
+            nearest_valid,
             exact_unclipped,
             column_overshoot_after_line_end,
         }

crates/editor/src/hover_popover.rs

@@ -1952,6 +1952,7 @@ mod tests {
             PointForPosition {
                 previous_valid,
                 next_valid,
+                nearest_valid: previous_valid,
                 exact_unclipped,
                 column_overshoot_after_line_end: 0,
             }
@@ -2079,6 +2080,7 @@ mod tests {
             PointForPosition {
                 previous_valid,
                 next_valid,
+                nearest_valid: previous_valid,
                 exact_unclipped,
                 column_overshoot_after_line_end: 0,
             }